It's been a few days that I'm trying to install the last Debian version on my pc, but after the installation is complete, at the reboot my pc goes to the bios and it seems that grub isn't installed in my hard disk

Welcome to LQ.My guess is that you installed grub to the boot sector of your Debian partition. It should have been installed to the MBR of the hard drive.Here are instructions on how to repair that using your installation cd in rescue mode.https://feeding.cloud.geek.nz/posts/rei ... le-debian/